Induction sealing, which is known as cap sealing, is a non-contact method of heating a metallic disk to hermetically seal the top of plastic and glass containers. This sealing process takes place after the container has been filled, for example, tablets, and capped. A closure is supplied to a bottler with an aluminum foil liner already inserted. A typical induction liner is multilayered. The top layer spaced apart from an opening of the container is generally a paper pulp that is generally spot-glued to the cap. The next layer is wax that is used to bond a layer of aluminum foil to the pulp. The bottom layer is a polymer film laminated to the foil. In existing capping technologies, after the cap or closure is applied to the opening of container, the container passes under an induction coil that emits an oscillating electromagnetic field. As the container passes under the induction coil, the conductive aluminum foil liner begins to heat. The heat melts the wax, which is absorbed into the pulp backing and releases the foil from the cap. The polymer film also heats and flows onto the lip of the container. When cooled, the polymer creates a bond with the container resulting in a hermetically sealed product. While neither the container nor its contents are negatively affected, this process is performed within a few seconds or faster. It is possible to overheat the foil causing damage to the seal layer or any protective barriers. This could result in faulty seals, even weeks after the initial sealing process,
In order to detect a defect in sealing, various thermography based systems have been suggested and the systems are most based on processing of thermal image data of cap sealing photographed by an infrared (IR) camera or IR imaging camera.
The IR camera or IR imaging camera detects energy of an IR wavelength range and converts the energy to an image. All objects emit an IR ray and an object having a higher temperature emits a larger amount of IR. Accordingly, an IR image may be understood to be a thermal image.
The IR camera may include a cooled type and an uncooled type. Generally, the cooled type IR camera is sensitive to a wavelength range of about 1 μm to about 5 μm and the uncooled IR camera is sensitive to a wavelength range of about 7 μm to about 13 μm. Factory calibration of an IR camera is performed by a manufacturer. In this process, the IR camera has a calibration table or a calibration file suitable for a particular temperature range.
When an appropriate calibration value is not loaded, incorrect temperature data is read. When a sudden temperature change of an external environment occurs, the temperature of an object to be photographed is changed. The physical quantity of temperature has the following properties. Even when a temperature value changes as a temperature environment is rapidly changed, the temperatures of objects in the environment are relatively slowly affected, compared to the temperature of the atmosphere, and the temperatures of the objects are changed. When the IR camera is in error, data is read and presented in an image, showing a different value from an actual temperature. These properties are important problems in the IR camera based image photographing performed through observation of thermal energy.